Process for making hollow metal articles having passageways



Oct. 16, R. F. ADAMS PROCESS FOR MAKING HOLLOW METAL ARTICLES HAVINGPASSAGEWAYS Filed Aug. 24, 1952 2 Sheets Sheet l IN VEN TOR: RICHARD F.ADAMS BY WWW Qct. 16, 1956 R. F. ADAMS 2,766,514

PROCESS FOR MAKING HOLLOW METAL ARTICLES HAVING PASSAGEWAYS Filed Aug.24, 1952 2 SheetsSheet 2 FIG. 4. I

Q II Willi)? INVENTOR: RICHARD F. ADAMS BY cmww AGENI 2,766,514-Patented Oct. 16, 1956 PROCESS FOR MAKING HOLLOW METAL ARTICLES HAVINGPASSAGEWAYS Richard F. Adams, Alton, Ill., assignor to Olin MathiesonChemical Corporation, a corporation of Virginia Application August 24,1953, Serial No. 376,133

1 Claim. (Cl. 29-1573) This invention relates generally to ametallurgical process and more particularly to a novel and improvedmethod for forming structural members and other cavitated articles froma plurality of sheets of metal.

In a process which involves welding preselected areas of the surfaces ofa plurality of strips of metal and thereafter inflating those areasbetween the welds by the application of fluid pressure, considerabledifficulty has been experienced in properly expanding such free spacesbecause each of the plurality thereof will not begin expandingsimultaneously and will not continue to expand uniformly. Consequently,one free space or area might expand into another free space before thissecond free space has expanded and will thus prevent it from properlyexpanding. Such a condition can usually be prevented in a structurefabricated from only three sheets wherein the,

free spaces to be expanded are separated by only one intermediate metalsheet by using two synchronized inflating instruments, one on each sideof the intermediate sheet. Synchronization of the fluid pressure is verydifiicult, however, and not always entirely accomplished.

'When cavities are to be formed in welded assemblies of more than threesheets the use of a plurality of inflating devices is even morediflicult and less satisfactory.

It is therefore an object of this invention to provide an improvedmethod for forming cavitated articles from metal strips. Another objectof the invention is to provide a novel assembly of metal sheets havingareas therein adapted for inflation by fluid pressure. A further object-of the invention is to provide an improved process for formingpartially hollow structural members and similar :articles by weldingcontiguous surfaces of a plurality of metal sheets in preselected areasand thereafter inflating the areas between the thus formed welds byfluid pressure. A more specific object of the invention is to pro: videan improved method for inflating the areas between a plurality of sheetsof metal having weld lines bordering said areas.

Further objects will become apparent from the following description withreference to the attached drawing in which Figure 1 illustrates metalsheets prior to assembly thereof to form one embodiment of theinvention, While Figure 2 is a longitudinal sectional View through theassembly of the sheets of Figure 1 at the position of line A-B;

Figure 3 is a cross-sectional view of the assembly of the sheets ofFigure 1 at the position C -D;

Figures 4 and 4a are cross-sectional views of piles of metal sheets atthe line C-D of Figure 1 after welding and partial inflation of theareas between welds and Figure 5 is a cross-sectional view at the lineC-D of Figure 1 after complete inflation of areas between welds.

In accordance with this invention the foregoing objects and advantagesare accomplished, generally speakfashion as to provide a partialoverlapping of the unwelded portions of adjacent pairs of sheetsurfaces. Thus, considering .a sheet intermediate between the top andbottom sheets, the unwelded portions on one side of said sheet would inpart overlap or be staggered in relation to the unwelded portions on theopposite side of said sheet, but none of such unwelded portions arecompletely overlapped by unwelded portions immediately above orimmediately below it in the pile. The free spaces or unwelded areasbetween welds communicate with the external surface of the assemblythrough a free space forming a common passage or header in order that asubstantially uniform fluid pressure can be applied to each area atsubstantially the same time to efiect expansion thereof.

Although the method of this invention is advantageous for the inflationof free spaces or unwelded areas of an assembly which has been welded byany suitable method.

including conventional torch welding methods, it is preferred to weldthe preselected regions of the face to face surfaces of juxtaposed metalsheets by pressure rolling methods such as by a hot roll bonding methodsimilar to that disclosed by Grennell in the copending patentapplication Serial No. 218,116, now abandoned, also the property of theassignee of this invention.

In accordance with such process, a suitably foreshortened pattern ofweld preventing material is interposed between adjacent surfaces of apile of metal sheets and this assembly is thereafter rolled at asuitable temperature and pressure to effect adequate reduction of thethickness of the metal sheets to weld the unprotected areas thereof. In.a preferred embodiment of the instant invention, prior to bonding thesheets in accordance with the Grennell process, the pattern of weldpreventing material or stop-off material is interposed between one pairof adjacent surfaces of juxtaposed metal sheets of an assembly of aplurality of at least three sheets in a position that only partiallyoverlaps the stop-off material which is interposed between anothersurface of one of the pair of sheets with a third metal sheet.

Many articles such as structural metal supports and similar members arecomposed of hollow channels or cavities which do not communicate witheach other but, on the other hand, extend for a considerable length orextend throughout the length of the member. In forming such articles bya preferred embodiment of this invening, by welding adjacent surfaces ina pile of metal sheets a 1 tion from say three sheets of metal, eachpart of the patterns of stop-0E material lying adjacent each side of theinterposed sheet continues into stop-01f material lying between the twoouter sheets of the assembly at least partially beyond the edge of theshorter interposed sheet. This area of the pattern lying beyond the edgeof the interposed metal sheet preferably continues at a predeterminedposition to the edge of the assembly. After pressure welding thoseregions of the sheets bounding the pattern, the metal sheets are priedapart at the locale of the pattern at the edge of the assembly. Asuitable instrumentality is inserted between the sheets by means of thethus formed opening and fluid pressure is introduced therethrough toexpand the free spaces lying between the welds.

The free space lying between welded areas of the two outer sheets andbeyond the edge of the layer formed by the interposed sheet will expandfirst and form a chamber or header which communicates with each of theother passages or spaces to be inflated. The free spaces lying on bothsides of the interposed sheet will not commence expandingsimultaneously. After one group begins expanding, further expansion ofthat group is apparently less diflicult than starting the expansion ofthe other group because those free spaces have thus started to bulge Junder the pressure will usually continue expanding until the wall of theconfining die is reached before the free spaces of the other group willbegin expanding.

The expansion of these free spaces will not only be in the directiontowards the sheet of metal adjacent thereto but will be also towards thesheet adjacent the other side of the interposed sheet. As a result, asthe expansion continues in this direction, that portion of theinterposed sheet bounding the free space which is directly opposite theexpanding space will be pressed more firmly against the adjacent sheetand subsequent expansion of the free space will become increasingly morediflicult, if not impossible. But, since in accordance with thisinvention, the pattern between one side of the interposed sheet and thesheet adjacent thereto does not entirely overlap the similar patternbetween the other side of the interposed sheet this condition is avoidedbecause that portion of the interposed sheet bounding the free space andnot overlapping a similar area on the opposite side of the sheet willnot be pressed more firmly against the adjacent sheet. Once expansion ofa free space is started, it can easily be continued until even thatportion of the space which was pressed against the adjacent sheet can beexpanded to conform with the configuration of the dies.

In order to further clarify and to better explain the invention, thefollowing is a description of an embodiment thereof with reference tothe drawing:

A pattern of a suitable stop-off material such as, for example, onecomposed of about 40 percent calcium carbonate having a granulation ofless than about 325 mesh, about 13 percent colloidal graphite, about onepercent wetting agent, and about 46 percent water is applied to asuitable clean surface of aluminum sheets 1 and 3 of Figure l bystenciling with a silk screen. Rectangular areas 8, 9, 10, 11, 12, and13 on sheet 1 each terminate intemally of edge 14 but extend into thearea 6 and to the edge of the sheet through passage 22. Rectangularareas 15, 16, 17, 18, 19 and 20 terminate internally of edge 21 of sheet3 but extend into area 24 and to the edge of the sheet through passage23.

Sheets 1, 2 and 3, each about 0.08 inch thick, are assembled so thatedges 14, 21 and 25 are substantially even with each other. Sheet 2 isshorter than sheets 1 and 3 and terminates within the area covered by 6of sheet 1 and within 24 of sheet 3, the resulting assembly beingsimilar to that shown in the cross-sectional view of Figure 2. This viewis of a section through the assembly at the line A-B. The rectangularareas 8, 9, 10, 11, 12 and 13 and areas 15, 16, 17, 13, 19 and 20 arelocated on sheets 1 and 3 respectively so that they do not entirelyoverlap each other. In other words, care is exercised to insure that thepattern on sheet 2 is moved to the right of sheet 3, as shown in thedrawing, a distance suificient to form a partially overlapping patternsuch as shown in Figure 3. Figure 3 is a sectional view through theassembly at line CD and shows the relative position of the two patternson opposite sides of sheet 2.

The resulting pile or assembly of sheets 1, 2 and 3 are spot welded in afew places or otherwise bound together to prevent slippage relative toeach other. The assembly is then heated in a suitable furnace to atemperature of about 890 F. and is immediately rolled in one pass toreduce the thickness of the assembly from about 0.24 inch to about 0.08inch. After cooling, the pile is rolled to further reduce'it to thedesired gauge 'of about 0.06 inch after which the assembly is annealedby heating in a suitable furnace at a temperature of about 650 F. forabout one-half hour.

During the hot rolling of the assembly, regions 27 and 28 of sheets 1and 3, respectively extending beyond edge 26 of sheet 2 are forcedtogether and the surfaces 29 and 30 of sheet 3 are welded to surfaces 31and 32 of sheet 1 to bound unwel'ded areas 24 and 6 except in theregions 22 and 23. In some instances where the amount of reduction willnot be sufficiently great to force the surfaces 4 of regions 27 and 28together and weld them, strips of metal of suitable thickness can beinserted between sheets 1 and 3 to cover only those surfaces 22, 23, 29,30, 31 and 32 of the sheets. In this way, each of sheets 1 and 2 will bewelded to the interposed strip of metal.

After welding has been completed, the passage between 22 and 23 is priedopen sutficiently to permit insertion of a suitable needle or othersuitable instrumentality for conducting a fluid such as compressed airinto the areas lying between the welds. The free spaces 6 and 24 willbegin expandin as pressure is applied and will form a header throughwhich additional fluid will pass to the rectangular passages or freespaces 8, 9, 10, 11, 12 and 13 between sheets 1 and 2 and passages orfree spaces 15, 16, 17, 18, 19 and 20 between sheets 2 and 3. Expansionof one or more of the free spaces on one side of the interposed sheet 3will ordinarily begin before free spaces on the other side of the sheetbegin expanding. The expansion of one of these thus started free spaceswill continue without expansion of an opposed space until a cavity isformed in the assembly as illustrated in Figure 4. For example, theareas might expand to the extent illustrated at 33 of Figure 4. In thisparticular instance the free space 33 has been distorted to the pointthat inflation of space 34 will require moving the metal of former sheet2 adjacent space 34 back towards the metal formerly sheet 1. If theentire free space on one side of the sheet is directly opposite a freespace on the other side, that is, if space 34 were directly below space33, inflation would be ex tremely diificult, if not impossible. Wherethe patterns are designed to not completely overlap each other, thatportion of the free space such as at 38 which extends beyond 37 ofFigure 441 will inflate without much difiiculty and once such expansionhas occurred it will continue into the distorted and sealed region 39also without much difficulty or without requiring the application ofexcessive pressures.

Figure 5 is illustrative of the type of product obtainable by theforegoing embodiment of the process of the invention after the weldedand inflated assembly has been trimmed to remove the headers 24 and 6and to remove the welded areas along edges 14, 25 and 21 to expose openends of the cavities which have been formed from free spaces 8, 9, 10,11, 12 and 13 and 15, 16, 17, 18, 19 and 20.

Hollow articles can be made from copper, copper alloys, titanium,zirconium, steel or similar metals as well as aluminum in accordancewith this invention and any stop-off" material capable of preventingwelding of juxtaposed surfaces can be utilized to form the pattern inlieu of the composition described in the foregoing embodiment. At leastabout 10 percent of the pattern should not overlap a pattern betweenface to face surfaces of juxtaposed metal sheets in order to insureoptimum expansion with a minimum of difliculty.

The amount of reduction required to effect welding of juxtaposedsurfaces will vary with the particular metal and the physical propertiesthereof. A reduction in thickness of at least per cent is suflicient forwelding most metal sheets but a greater percentage reduction may berequired for welding some metals.

Sheets of one metal can be welded to sheets of another metal inaccordance with this invention to make hollow articles particularly wellsuited for specialized purposes. However, the various kinds of metalchosen to form such a composite structure must have physical propertieswhich will permit heating the assembly to a temperature above therecrystallization point of all metals utilized without melting any oneof the sheets. By heating the metal above the recrystallizationtemperaature thereof and reducing the metal in accordance with thepreferred methods of this invention a substantially complete erasure ofthe interface between sheets of metal by interdispersioneof the grainsof one sheet with those of the adjacent sheet is obtained. The resultingjuncture is usually characterized by a tensile strength equal that ofother regions of the metal sheet.

The sheet of metal interposed between a pair of sheets can terminateanywhere within the free spaces 6 and 24 but must not extend into areas31, 32, and 29 and 30. If the interposed sheet does terminate beyond thespecified region, the free spaces on one side of the exposed sheet willoften expand first and will force the interposed sheet so tightlyagainst the member of the assembly between which expansion has not begunthat expansion will be almost impossible. In other words, if the freespaces of the illustrated assembly between sheets 1 and 2 expand first,the edge of interposed sheet 2 will often be forced against surfaces 29and 30 of sheet 3 so tenaciously that expansion of the free spacesbetween sheets 2 and 3 will be very difficult or almost impossible. Ifthe interposed sheet terminates short of the juxtaposed pair of sheetsand within the area communicating with all other passages of theassembly distortion of part of the assembly by expansion of the other isavoided and expansion of all unwelded areas or free spaces can beaccomplished by applying fluid pressure through the header thusprovided.

For convenience much of the foregoing description is with reference to apile of three sheets in which one sheet is interposed between two sheetsof greater dimen- I sion. The invention is not limited, however, to apile consisting of three sheets but is equally applicable to multiplesthereof or to piles containing various numbers of sheets. As indicatedhereinbefore, where the number of interposed shorter sheets or thethickness thereof are such that the distance between the overlappingends of the pair of sheets is too great for the surfaces thereof to beforced together and to be welded in those areas bounding the pattern toform free spaces from which the header can be formed, suitable strips ofmetal are inserted to cover those areas bounding the pattern and face toface surfaces of the strips and sheets are thereafter welded together.Thus, in this way, several shorter sheets may be interposed between twolonger sheets.

While embodiments of the invention have been described in detail, thisdescription is only illustrative and many changes may be made therein bythose skilled in the art without departing from the spirit and scope ofthe invention as set forth in the appended claim.

The word sheet is used in the appended claim to define a piece of metalwhich is very thin in relation to its length and breadth and free spacedenotes an unwelded area of metal lying between welded areas of adjacentsurfaces of two sheets.

Having thus described the invention, what is claimed and desired tosecure by Letters Patent is:

A method for making hollow articles having passageways lying one abovethe other comprising, forming a stack of at least three sheets of metalwith the two outer sheets longer than the intermediate sheets, andsimultaneously sandwiching between one side of an intermediate sheet andthe adjacent sheet a series of bands of stop-0E material and a similarseries of bands of stop-off material between the other side of theintermediate sheet and the adjacent sheet with each of the bands of oneseries staggered with respect to each of the bands of the other seriesand overlapping not more than percent thereof, said bands terminatinginternally of the edges of the stack at one end and all leading into acommon transverse band at the other end that lies between the two outersheets and beyond the end of the intermediate sheet but terminatesinternally of the edges of the outer sheets; securing the sheets againstrelative movement, forge welding by rolling the areas of theintermediate sheet and adjacent sheets bordering said bands and theareas along the edges of the longer sheets bordering the transverseband, and thereafter directing fluid pressure into the common transverseband to expand the unwelded areas adjacent said stop-01f material,whereby the outer sheets are moved apart and the intermediate sheet isdeformed.

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